I think folks may want to rewatch that fight scene between Spock and Khan. Spock was getting his ass handed to him until Uhura beamed down and phasered Khan. And she was the one who stopped Spock from outright killing Khan because they needed his blood to save Kirk.
She saved the day.
I think that if anyone else had beamed down, Spock kills Khan.
Actually Khan would have killed Spock. Spock seems to have a lot of endurance when he fights but he still would have lost the fight.